The invention relates to branched polyamines for delivery of biologically active materials, and more specifically, to carbamate functionalized branched polyethylenimines comprising hydrophobic carbamate end groups for gene delivery.
Nucleic acid-based therapy holds great promise in treating human diseases. In principle, not only can faulty and defective genes be corrected and replaced by functional ones, but redundant gene expression could also be repressed to normal level by the use of RNA interference. In general, there are two major types of gene delivery vectors, viral and non-viral vectors. Although viral vectors have superior transduction capabilities, the immunogenic and oncogenic potential of viral vectors limits their clinical applications. To circumvent this problem, a number of non-viral gene delivery systems have been reported, which include (1) complex of nucleic acids with various cationic molecules including lipids, polymers and peptides and (2) conjugation of nucleic acids with natural ligands such as, for example, cholesterol and cell penetration peptide. Non-viral gene delivery vectors are receiving increasing attention due to biosafety, low production cost, ease of transportation and storage, reproducibility, and tunable functionalities for targeting specific cell types.
Among the various types of non-viral vectors branched polyethylenimine (bPEI), which contains primary, secondary and tertiary amine groups, provides high gene transfection efficiency in vitro. In particular, bPEI having a weight average molecular weight (Mw) of about 25 kDa and number average molecular weight (Mn) of about 10 kDa, referred to herein as bPEI-25, is regarded as an industry standard. bPEI-25 has a high cationic charge density at physiological pH, where about 20% of amine groups (i.e. primary amines) of bPEI-25 are protonated. This allows bPEI-25 to interact electrostatically with negatively charged nucleic acids over a broad pH range and to complex them into nanoparticles. Once bPEI-25/nucleic acid nanocomplexes are internalized by the cells, the secondary and tertiary amines facilitate the release of the nucleic acids from the endosomes through the “proton sponge effect”. In the case of deoxyribonucleic acid (DNA), the uptake of the released nucleic acids into the nucleus confers high gene transfer efficiency.
Despite its high gene transfection efficiency, the net positive charge of bPEI-25 has major drawbacks concerning toxicity, aggregation and undesired non-specific interactions of bPEI-25/nucleic acid complexes with cellular and non-cellular components, particular in vivo. Adverse effects include liver necrosis, adhesion of aggregated platelets and shock after systemic injection of higher doses.
In view of the cytotoxic issues faced by bPEI-25, low molecular weight branched polyethylenimine (Mw about 2.0 kDa, Mn about 1.8 kDa, referred to herein as bPEI-2) has gained interest as well due to its favorable cytotoxicity profile. Low molecular weight enables bPEI-2 to be excreted from the kidneys when used for in vivo therapeutic purposes. However, the major disadvantage of bPEI-2 is its inefficient transfection ability rendering it inadequate for use as a gene transfection vector.
Thus, an ongoing need exists to develop more efficient and less cytotoxic polyethylenimine derivatives for delivery of biologically active materials.